Extreme pressure grease with improved wear characteristics

ABSTRACT

Grease composition: A. LUBRICATING OIL BASE B. GREASE THICKENER C. 1-15 PERCENT MOLYBDENUM DISULFIDE D. 1-15 PERCENT CALCIUM HYDROXIDE.

United States Patent Green Oct. 29, 1974 1 1 EXTREME PRESSURE GREASE WITH IMPROVED WEAR CHARACTERISTICS [52] US. Cl 252/21, 252/25, 252/28 [51] Int. Cl..... Cl0m 5/22, ClOm 5/02, Cl0m 7/06 [58] Field of Search 252/21, 25, 28

[56] References Cited UNITED STATES PATENTS 5/1943 McLennan et a1 252/21 7/1954 Zojac 252 25 1/1964 Rees et a1. 252/21 3,344,065 9/1967 Gansheimer et a1 252/25 3,654,171 4/1972 Emond et a1. 252/28 Primary Examiner-Daniel E. Wyman Assistant Examiner-l. Vaughn Attorney, Agent, or Firm-T. H. Whaley; C. G. Ries [57] ABSTRACT Grease composition:

a. lubricating oil base b. grease thickener c. 115 percent molybdenum disulfide d. 1-15 percent calcium hydroxide.

4 Claims, No Drawings EXTREME PRESSURE GREASE WITH IMPROVED WEAR CHARACTERISTICS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention concerns the field of grease compositions.

2. Description of the Prior Art Greases are often required to possess properties in addition to lubricity. In operation of heavy equipment, such as the walking cam on a large drag-line, one of the more important properties is the ability to prevent welding, seizure and wear of metal surfaces sliding under extremely heavy loads. This property is referred to as the extreme pressure (EP) characteristic of the grease.

Many materials have been found which will improve the EP characteristics of a grease when added in small amounts. Some of these appear to function by reacting with the metal surfaces to form coatings which will not seize and weld when the pressure becomes so great that the oil film, which normally separates the surfaces, is broken. These additives generally are organic compounds containing reactive elements such as chlorine, sulfur and/or phosphorous. Some also contain metals such as lead or antimony which apparently enter into the surface coating. Antimony dialkyldithiocarbamate used in some of the grease compositions discussed herein is a material of this type. Although these additives are very effective EP agents, many of them tend to be corrosive and they frequently lead to high wear rates since the surface coatings they produce shear away rather than weld or seize as would be the case without the additive.

Another type of EP agents are finely ground, inorganic solids which apparently are not as easily forced from between the sliding surfaces as the oil film and therefore keep the metal surfaces from welding or seizing until the oil film can be restored. Unfortunately, these solids tend to be abrasive and therefore increase wear. One of the best and more widely used EP additives ofthis type is molybdenum disulfide; however, the art recognizes that even molybdenum disulfide increases abrasivcness, see US. Pat. No. 3,396,108 1968) to Caruso.

Applicant has discovered a method of retaining the extreme pressure properties of molybdenum disulfide while greatly reducing the abrasiveness.

US. Pat. No. 3,344,065 (l967) to Gansheimer, et al., discloses What they consider to be a list of equivalent additives for greases including molybdenum disulfide and hydroxides of calcium. Examples in this patent show calcium hydroxide and molybdenum disulfide used separately as additives in grease formulations.

Surprisingly, Applicant has discovered that molybdenum disulfide and calcium hydroxide are not equivalent as taught in the Gansheimer reference, and that, in

fact, a combination of molybdenum disulfide and calcium hydroxide in a grease will impart excellent extreme pressure or load carrying characteristics and provide low abrasion and consequently excellent wear characteristics.

SUMMARY OF THE lNVENTION The invention is a grease composition comprising a lubricating oil, a thickener of soap or clay, and a combination of molybdenum disulfide and calcium hydroxide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS compositions generally. Such oils include the conventional mineral lubricating oils having Saybolt Universal viscosities in the range from about seconds at F. to about 225 seconds at 2l0F., which may be either naphtenic or paraffinic in type or blends comprising both naphthenic and paraffinic oils. The preferred lubricating oils are those having Saybolt Universal viscosities in the range from about 300 seconds at 100F. to about 100 seconds at 210F., which may be blends of lighter and heavier oils in the lubricating oil viscosity range. Synthetic lubricating oils, which may be preferred in preparing greases having special properties required for special types of lubricating service, include oils prepared by cracking and polymerizing products of the Fischer-Tropsch process and the like as well as other synthetic oleaginous compounds such as polyethers, polyesters, silicone oils, etc. having viscosities within the lubricating oil viscosity range. Suitable polyethers include particularly polyalkylene glycols such as polyethylene glycol. Suitable polyesters include the aliphatic dicarboxylic acid diesters, such as di-2-ethylhexyl sebacate, di (secondary amyl) sebacate, di-2- ethyl-hexyl azelate, di-iso-octyl adipate, etc. The sulfur analogs of the polyalkylene esters and polyesters are also suitable.

Silicone polymer oils may also be employed, preferably having viscosities in the range from about 70 to 900 seconds Saybolt Universal at 100F. Suitable compounds of this type include dimethyl silicone polymer, diethyl silicone polymer, methyl cyclohexyl silicone polymer, diphenyl silicone polymer, methylethyl silicone polymer, methyltolyl silicone polymer, etc.

Generally two types of thickeners for the oils are used to form greases: soaps and/or clays.

By the term soap-base thickening agent," as used herein, is meant metal soaps of fatty acids which are capable of providing a stable gel structure to lubricating base oils. The term is intended to include conventional metal soaps, complex soaps, mixed base soap greases, and the like, and includes the following particular types of soap thickeners:

. Metal base:

Aluminum base Barium base Calcium base Lithium base Sodium base Lead base Strontium base Mixed bases:

Sodium-calcium base Sodium-barium base Calcium-aluminum base Sodium-aluminum base 3 Magnesium-aluminum base Lithium-aluminum base Lithium-calcium base Metal complex:

Hydrated calcium soap Hydrated aluminum soap Hydrated barium soap Hydrated lithium soap Hydrated sodium soap Hydrated strontium soap Complex aluminum soap Complex barium Soap Aluminum-barium complex Aluminum-sodium complex Complex calcium soap Calcium soap-calcium acetate complex Calcium soap-calcium chloride complex Calcium soap-strontium hydrate complex Calcium-barium soap complex Complex lithium soap Lithium soap-lithium acetate Lithium soap-lithium azelate complex Magnesium soap complex Lead soap complex Sodium soap-sodium acetate complex Sodium soap-sodium acrylate complex Sodium-barium complex Strontium-calcium acetate complex Though the lubricating base oil component of the invention can be either a natural or synthetic oil, as a practical matter, the base oil will usually be a natural oil, e.g., a petroleum-derived mineral oil. Many synthetic oils such as silicone oils and various esters can be thickened effectively with soap thickeners; however,

the thermal stability of. soaps is usually considerably lower than that of the synthetic oils. Therefore, there is usually no point in using expensive synthetic oils with soap greases. Exceptions to this, however, are some of the complex greases which possess considerably higher thermal stability than the conventional soap-base greases.

The clays which are useful as thickeners for the preparation of greases are oleophilic clay products exhibiting a substantial base exchange capacity. The clays particularly contemplated herein include especially the montmorillonites, such as sodium, potassium, lithium, and the other'bentonites, particularly of the Wyoming bentonite type. Still more preferred are the magnesium bentonites, sometimes referred to as Hectorites. These clays are characterized by unbalanced crystal structure and are believed to have negative charges which are normally neutralized by inorganic cations.

The term oleophilic clay product is meant to include such clays when they have absorbed thereon or reacted therewith sufficient organic ammonia base to form an oleophilic product. The so-called oniumclays" comprise reaction products of oleophilic ammoniumbases (or their salts) and clay.

The clays are more preferably modified by absorption of one or more oleophilic cationic surface-active agents such as those described in US. Pat. Nos. 2,831,809, and 2,875,152.The clays are preferably present in an amount sufficient to cause grease formation of the lubricating oil to occur. This will usually occur in the range of 25-10 percent by weight of the high base exchange clay (based on the inorganic clay portion of the oleophilic clay product) depending somewhat upon the precise clay employed, the chem cal constitution of the major lubricating oil components and the proportions of other components present in the grease formulation.

In addition to the additive combination of my invention, other additives of the types ordinarily employed in lubricating compositions may be employed in these fates or sulfonates, imidazolines of the type of 1- betahydroxyethyl-Z-tallowimidazoline, etc. Other extreme pressure additives include, for example, sulfurized or chlorinated fatty oils, sulfurized diisobutylene, chlorinated paraffins, lead naphthenate, lead diamyldithiocarbamate, antimony dialkyldithiocarbamate, antimony phosphorodithioate. Additives of each of the above types are ordinarily employed in the composition in amounts from about 0.1 to about 5.0 percent, and most suitably in amounts from about 0.2 to about 2.0 percent by weight.

The additive combination of my invention: molybdenum disulfide and calcium hydroxide should be employed in the following weight percentages of the grease and ratios to each other. Both broad acceptable ranges and more narrow preferred ranges are given.

Four bentonite thickened mineral oil greases were prepared containing molybdenum disulfide alone, molybdenum disulfide and calcium carbonate and molybdenum disulfide and hydrated lime or calcium hydroxide. The greases were tested for load bearing ability and wear resistance. The results showclearly that load wear index and weld point values measure of extreme pressure properties were not affected adversely by lime addition but that the wear tests were greatly improved when both molybdenum disulfide and lime were used.

BATCH NO. 33 l8-Rl. 33 lfi-RL PA-l88l PA-2262 Composition, WW1

Dimethyldioctadecyl ammonium bentonite 4.2 4.3 5.7 8.0 Mineral Oil 84.8 81.7 80.3 78.0 Antimony dialkyldithiocarbamale 4.0 4.0 4.0 4.0 Molybdenum disulfide 7.0 7.0 7.0 7.0 Calcium carbonate 3.0 Hydrated Lime 3.0 3.0 Penetration Worked. 60 strokes 360 367 384 375 Load Carrying Ability Load Wear Index 70.3 82.2 M8 748 Weld Point. Kg 2 282 282 282 Wear Modified Timken Wear Test Ampco C-3 Block Sear, MM 8.3.7.3 7.3.6.4 3.6.3.6 2.93.4

Navy Gear Wear Brass On Steel 5 lb Load my loss/1.000 cycles l.l5 0.47 0.30,0.l5 0.30

l lb Load my loss/l .000 cycles 24 l.7 0.53.0.30 l.25 Four Ball Wear Scar. MM 0.60 0.49 0.54 .53

Example 2 nation of molybdenum disulfide and calcium hydroxide A grease composition as shown below was prepared and tested in field operations as a walking cam lubricant. The lubricant has successfully performed for eight months.

Composition. Wt.'/:

Mineral. oil Dimcthyldioctadecyl ammonium bentonite Hydrated lime Molybdenum disulfide Antimonydialkyldithiocarbamate Load Wear index. Kg Weld Point. Kg Four Ball Wear I800 RPM, l30F.. Scar, MM

Navy Gear Wear lb load, wt.

loss/ 000 cycles. mg.

lb load, wt. loss/ I .000

cycles, mg.

wherein the weight ratio of molybdenum disulfide to calcium hydroxide is from about 0.5 to about 10.

2. A grease as in claim 1 wherein the molybdenum disulfide comprises from about 1 to 15 weight percent of the total grease composition and the calcium hy droxide comprises from about 1 to 15 weight percent of the total grease composition.

3. A grease as in claim 2 wherein the molybdenum disulfide comprises from about 2 to 10 weight percent of the total grease and the calcium hydroxidecomprises from about 2 to 6 weight percent of the total grease and the weight ratio of molybdenum disulfide to calcium hydroxide in the grease composition is from about 1.0 to 5.0.

4. A grease as in claim 3 which comprises 'a mineral lubricating oil comprising about weight percent of the total grease,

dimethyldioctadecyl ammonium bentonite thickener comprising about 6 weight percent of the total grease, 1

calcium hydroxide comprising about 3 weight percent of the total grease,

molybdenum disulfide comprising about 7 weight percent of the total grease and antimony dialkyldithiocarbamatecomprising about 4 weight percent of the total grease. 

1. A GRASE LUBRICATING COMPOSITION COMPRISING A LUBRICATING OIL VEHICLE, A THICKENER THEREFOR, AND AN EXTREME PRESURE AND WATER REDUCING AMOUNT OF A COMBINATION OF MOLYBDENUM DISULFIDE AND CALCIUM HYDROXIDE WHEREIN THE WEIGHT RATIO OF MOLYBDENUM DISULFIDE TO CALCIUM HYDROXIDE IS FROM ABOUT 0.5 TO ABOUT
 10. 2. A grease as in claim 1 wherein the molybdenum disulfide comprises from about 1 to 15 weight percent of the total grease composition and the calcium hydroxide comprises from about 1 to 15 weight percent of the total grease composition.
 3. A grease as in claim 2 wherein the molybdenum disulfide comprises from about 2 to 10 weight percent of the total grease and the calcium hydroxide comprises from about 2 to 6 weight percent of the total grease and the weight ratio of molybdenum disulfide to calcium hydroxide in the grease composition is from about 1.0 to 5.0.
 4. A grease as in claim 3 which comprises a mineral lubricating oil comprising about 80 weight percent of the total grease, dimethyldioctadecyl ammonium bentonite thickener comprising about 6 weight percent of the total grease, calcium hydroxide comprising about 3 weight percent of the total grease, molybdenum disulfide comprising about 7 weight percent of the total grease and antimony dialkyldithiocarbamate comprising about 4 weight percent of the total grease. 